Avoid duplication in docstring

Co-authored-by: Jon Duckworth <jon@radiant.earth>

Author: lossyrob

pystac/stac_object.py

@@ -512,7 +512,7 @@ def from_dict(
                 during this method call. Otherwise the dict is not mutated.
                 Defaults to True, which results results in a deepcopy of the
                 parameter. Set to False when possible to avoid the performance
-                hit of a deepcopy. Defaults to True.
+                hit of a deepcopy.
 
         Returns:
             STACObject: The STACObject parsed from this dict.